This invention pertains to the art of detecting means and more particularly to means for detecting whether a member is rotating relative to a fixed position. The invention is particularly applicable to an electric vacuum cleaner employing a rotating beater brush and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.
Typically, a rotating beater brush is employed in an electric vacuum cleaner for agitating the floor surface and assisting in removal of soil and dirt therefrom. An electric motor is supplied with a source of alternating current, such as obtained through a conventional household electrical outlet. Rotary motion of the motor is advantageously used to create a vacuum effect at a nozzle area. Additionally, an elastomeric belt extends from the main motor to drive the brush. The beater brush includes radially outward extending bristles that mechanically sweep the floor surface and assist in loosening dirt and debris. Therefore, the floor surface is cleaned through use of the vacuum or suction action in combination with the mechanical action of the brush.
Actuation of the motor normally signifies that the brush is also rotating. Occasionally, though, the brush fails to rotate even though the motor is operating. For example, the belt will fail either by jamming of the brush bearings with dirt, by wear of the belt, by separation from the motor driveshaft, or by simply breaking. In such cases, the operator of the vacuum cleaner may not be aware that the brush fails to rotate, or that it is rotating at insufficient speed, since there is no readily visible indicator or detector means.
U.S. Pat. No. 4,392,271 issued to Sepke July 12, 1983, is directed to one potential solution to the above-identified problem. More specifically, Sepke contemplates use of a transparent window mounted in an upper portion of a nozzle housing. The window is aligned with an elastomeric drive belt to enable an operator to visually determine the condition of the belt. The outwardly facing surface of the belt is provided with light colored markings which are readily contrasted with the dark color of the remainder of the belt. These markings are such that alternate regions of the markings and the belt will be visible so that movement is readily detectable.
One apparent problem with this structure resides in the environment and use of the vacuum cleaner. Dirt and debris can cloud the transparent window after extended use. Further, although rotational and stationary conditions of the belt can be easily detected, there is no means to distinguish between predetermined rotational speeds of the belt in an accurate manner. Slippage or wear of the belt may not be apparent until the brush is rotating at an extremely slow speed or not at all.
It has, therefore, been considered desirable to provide a new detecting means that is not subject to the above identified problems and yet offers all the same benefits. It has also been considered desirable to provide a means for readily detecting predetermined rotational speeds of the beater brush. The subject invention is deemed to meet these needs and others in a simplified and economical manner.